Unexpectedly high mortality of Eastern Red Cedar has been observed this spring and summer across parts of Iowa, Missouri, Illinois, and Kansas. The underlying cause has been difficult to pin down, but these state summaries reveal some common features.
Missouri: Initial field visits showed that some trees in Columbia and Piedmont, Mo., were infected with Heterobasidion annosum. In areas with annosum root rot, the disease appeared to follow a typical root disease pattern with an identifiable “center” and damage spreading outward. Visits to the Kansas City and Kirksville, Mo. areas, showed no sign of root disease, and attempts to consistently isolate pathogenic fungi from affected trees proved inconclusive. Most eastern red cedar mortality reports from northern and western Missouri have been from the Kansas City and St. Joseph areas. The typical symptom was a relatively healthy tree that turned olive green and then completely brown within two weeks. Basal cankers, collar rots, or root rots were not observed on most trees. Trees tended to be randomly distributed. Affected windbreak trees seemed to be growing in soil similar in structure, aspect, drainage, and compaction to that of healthy trees. In general, mortality did not appear to be spreading to neighboring trees. Most affected cedars have been fairly young (5 to 20 years old) in both planted windbreaks and natural stands. A relatively low percentage of trees are actually affected in most property situations (i.e., less than 1 percent), but some properties have higher mortality rates (i.e., up to 5 percent). Most trees died early this spring, but red cedars are still dying, according to reports from north-central Missouri. The only consistency found in affected trees was the presence of extremely high numbers of bark beetles. Bark beetle infestations may be the eventual cause of death, but something else is suspected to have caused them to attack apparently healthy trees.
Northeast Kansas: Mortality has affected primarily windbreak trees, generally with less than 5 percent of trees affected on any given site. The condition showed up in late April/early May as off color and defoliation. Trees were dead within a couple of weeks. Excavated root systems look healthy, with no pathogens identified. Abiotic causes are suspected.
Iowa: in late April, Iowa Department of Natural Resources received reports of eastern red cedar and white cedar (arborvitae) declining statewide. Symptomatic trees started out healthy, turned pale green, and completely browned by the second week in May (in about a 2-weeks). The decline has continued to be reported within the state. Several fungal infections have been identified on declining trees including Pestalotia twig blight (Pestalotiopsis spp.), Berckmann’s blight (Seimatosporium berckmanssii), Phomopsis twig blight (Phomopsis juniperovora), and Kabatina blight (Kabatina juniperi). These fungal blights were identified on the branchlets and foliage, but not on established twigs. In addition, 12 of the 173 trees that were destructively sampled had annosum root rot (Heterobasidion annosum).
The abrupt mortality, widespread distribution of the mortality throughout the state, and the fact that the declining trees did not have one pathogen uniformly found on the declining trees indicates that other factors may be involved. Most of the trees sampled had evidence of bark beetle activity. Typically bark beetles are considered a secondary pest on junipers, but all of the affected trees had some bark beetle activity. The damage seems sporadic, with only a few trees affected in a windbreak planting. Iowa plans to continue looking into the problem and will begin scouring roots and other plant tissues to detect signs of nematodes. Nematodes have not been identified at this time.
Conclusion and Recommendations: Some cedars are being killed by annosum root rot, but a common cause of death appears to be bark beetle attacks following other stressors. If no other damaging agents are determined, the mortality may be a result of the various fungal diseases thriving during this cool moist spring, along with bark beetle attack. Pathologists will continue to follow the problem, keeping in mind that the mortality could be a result of the unusual weather events and that the problem may subside once “normal” weather returns. The current management recommendation is to remove and completely destroy dead and dying junipers. Trees that are already heavily infested with bark beetles will not recover, and sanitation will reduce emerging beetle populations, as well as destroying the fungal pathogens that may be present on the foliage.
The above was reprinted from the Central States Forest Health Watch, July 17, 2009. Thank you to Tivon Feeley (Iowa), Mark Schall (Missouri), and Megan Kennelly (Kansas) for sharing this information.